With the recent advancement of compression techniques of audio data such as music data, removable media including optical discs (hereinafter, simply “recording media”) can now store audio data corresponding to a lot of songs. Examples of the audio data compression techniques include MP3 (MPEG-1 Audiolayer-III) and WMA (Windows Media Audio). With the increase in the number of songs a recording medium can hold, some functions are becoming increasingly common. One example is a function of displaying information about the songs stored on the recording medium.
More specifically, with such a function, a list of the titles of songs stored on the recording medium is displayed, so that a user is allowed to select a song from the list for playback.
At the time when a recording medium is loaded in a playback device, the playback device reads and stores necessary data from a recording medium to its internal memory in advance, in order to display a list of songs stored on the recording medium or to play back of a song immediately upon a user request (For details, see the “Comparative Study with Conventional Playback Technology” section provided below). Also, there is disclosed a technique of checking such a playback device for memory corruption (JP patent application publication No. 2003-15963).
In addition, with the prevalence of portable devices capable of storing and playing audio data such as music, it is common to load a recording medium storing numerous songs in a portable device and plays back music, while carrying the device around.
During playback of music with a playback device being carried around, the playback device may momentary fail to read audio data from a recording medium because of shock or vibration given to the playback device. In view of such possibilities, audio data is read ahead into a memory of the playback device and the audio data is supplied from the memory for playback. This arrangement helps to play back audio data without skip or interruption (For details, see the “Comparative Study with Conventional Playback Technology” section provided below).
However, with increase in the amount of audio data such as music stored on a recording medium, the memory of the playback device is required to store a larger amount of data in order to display a list of stored music. Since the capacity of the memory is limited, a less area is allocated for storing read-ahead music data. This increases the possibility that audio playback gets interrupted.
Yet, by allocating a larger memory area to store audio data for the purpose of ensuring seamless audio playback, the playback device display may fail to display a list of songs or take relatively a long time before playback of a requested song starts. Such a playback device is poor in usability and practicability.
Yet, increasing the memory capacity will lead to increase the cost of playback device.